In a battery charging process, a charging IC is generally provided for supplying a charging current to a battery to be charged, and a resistor is generally used for providing a set voltage to the charging IC to set a required charging current, so that when different charging currents have different requirements, it is necessary to use a plurality of resistors to provide different set voltages.
With reference to FIG. 1 for a circuit block diagram of a conventional charging device and a battery, the conventional charging device comprise a control unit 10, a set voltage providing circuit 20, and a charging IC 30. The set voltage providing circuit 20 is coupled between the control unit 10 and the charging IC 30. The set voltage providing circuit 20 is controlled by the control unit 10, and each switching transistor T1, T2 is controlled to be turned ON and OFF by the received control signal switching transistor T1, T2 to provide different combinations for resistors R1˜R3, so as to provide different set voltages to a current setting terminal Iset of the charging IC 30, and the charging IC 30 can output a charging current Io from a current output terminal Out to a battery 40 according to the set voltage of the current setting terminal Iset.
In FIG. 1, a general charging system requires more resistors and switching transistors coupled to an integrated circuit to meet the different requirements of the charging current, thus incurring a higher cost and a larger area of the set voltage providing circuit 20. Therefore, another conventional programmable specific charging IC is introduced, wherein various different charging currents are provided directly according to a control signal of the control unit 10, such as an I2C high-performance charging device. However, the cost of such charging device is even higher.